Dr. Robbins participates in the NCI project studying the thyroid effects of the nuclear power reactor accident in Chernobyl. The case-control study on children in Belarus who developed thyroid cancer has been published ( Astakhova et al, Radiation Research 150, 349-356, 1998) and demonstrated a clear relationship between the estimated thyroid radiation dose from I-131 and the cancers. The prospective study of cohorts of children in Belarus and Ukraine is now proceeding in both countries and screening is under way in Minsk, Gomel and Kiev. The design and methods of the cohort study have been published (Radiation Research 161:481-492, 2004). Four biennial screening cycles are nearing completion. The end points include thyroid neoplasia, both benign and malignant, thyroid autoimmune disease, and hyperparathyroidism. The prevalence of thyroid cancer in the first cycle in Ukraine has been published (Tronko et al,JNCI 98:897-903,2006). A strong association of thyroid cancer and the individual thyroid radiation dose from I-131 has been demonstrated giving an Excess Relative Risk of 5.2 per Gray. A workshop on the potential effect of iodine deficiency on thyroid cancer risk was held and was published (Robbins et al, Thyroid, 11:487-491, 2001). Analysis of urine iodine excretion in the Ukrainian cohort during the first two cycles has been completed (Tronko et al, Thyroid 15:1291-1297, 2005) and demonstrates mild to moderate iodine deficiency, more pronounced in rural areas. Initial results on autoimmune thyroid disease in Ukraine has shown a significant radiation dose-response relationship for elevated serum antibody to thyroid peroxidase (antiTPO) but not for the prevalence of autoimmune thyroiditis (Tronko et al, J Clin Endocrinol Metab in press).